The main thrust of this program is to provide research training for a minimum of 2 1/2 years in pulmonary biology for M.D. and Ph.D. candidates at the postdoctoral level as they prepare to pursue academic research careers in biomedical sciences. The research trainees for the most part will come from the 9 clinical fellows selected each year for the Harvard Pulmonary and Critical Care Program. Each potential trainee, with guidance from the program directors, will spend up to 4 months visiting investigators and laboratories to choose a well-defined topic of investigation. The trainee will then work with a senior research mentor to develop a research project including a testable mechanistic hypothesis, which will be presented to the training grant directors for review and approval. Once the project is approved the trainee will work with that mentor for the duration of training. An outstanding faculty of 19 (both MD's and PhD's) is drawn from basic science and clinical departments. The primary focus of the training is in the Pulmonary and Critical Care Unit of the Department of Medicine at Massachusetts General Hospital, but can occur anywhere in the Harvard system such as at the Broad Institute shared with MIT. Four specialized research groups, cellular and molecular biology of lung injury, occupational medicine and molecular biology, lung inflammation, and positron emission tomography, provide each trainee a more cloistered and focused environment depending on their selected research project. The senior mentor will closely monitor the trainee's progress, with periodic review by program directors. An outside scientific advisory committee will review the entire program annually including movement of the trainee to become independent of their mentor. A course in Responsible Conduct of Scientific Investigation is required of all trainees. Specific courses in Biology of the Respiratory Tract, Epidemiology and Biostatistics, Ethics and Clinical Effectiveness will be offered as part of the training. An interactive, multi-disciplinary internationally recognized faculty provides a strong and exciting intellectual environment for research. At the conclusion of the training period, each trainee will have become adept and have appropriate expertise in one of the fields identified above, such as lung cancer or asthma, to be able to compete for further training or research support in an academic environment in biomedical research.